The effect of exchanging selected aryl and alkyl ammonium cations for sodium ions on the morphology and the hydrophobicity of a sodium montmorillonite was studied. It was found that the morphology of the organo-clays as observed by transmission electron microscopy depended on the type of and the amount of exchanged organic cation. An attempt was made to correlate the observed morphology of organo-clays with their hydrophobicity.

The standard method of assessing the available portion of the nutrient reservoir of a forest soil is to use a neutral salt solution, such as NH4OAc, to extract the exchangeable plus dissolved ions, which are analyzed and considered available. This approach, designed for evaluating nutrients available for the short growth term of agricultural crops, is inadequate for assessing the nutrient pool of forests where tree growth term may reach 100 yr or more.

Soil nutrient reservoirs were evaluated in two forest soils for K, Na, Ca, Mg and Fe, using an approach based on continuous extraction of the elements and kinetic analyses of the extraction rate curves. The analyses of the curves indicate that K, Na, Ca and Fe are each released at four separateconstant rates, and Mg is released at three separate constant rates. By analogy with similar kinetic studies done on monomineralic layer silicate samples, each separate extraction rate is thought to correspond to a single type of bond site in the soil. Higher extraction rates indicate greater ease of removal and are interpreted as indicating a higher degree of availability relative to the extractant.

The available K reserves of the Everett soil evaluated by standard methods, compared with annual net K uptake rates of its forest system, indicates growth limiting K deficiency in 12–17 yr. K availability assessed by kinetic analyses indicates about 100 yr supply of K is available.

An ambiguity in interpretation of electron micrographs of replicas of fracture surfaces of dry clay samples is illustrated, and a method of making ultra-thin sections described. Micrographs of ultra-thin sections of remoulded, consolidated, and sheared kaolin specimens are shown. In unconsolidated specimens random arrangements of particles, or of small groups of particles, were found. In failure zones, in sheared samples, the preferred orientation was parallel to the zone, with, in some cases, a subsidiary zone in which particles were inclined to the main zone. Interparticle contacts were mainly edge-to-edge or face-to-face.

It is common knowledge that the Jews have shown an unusually persistent emotional attachment to their fatherland, notably when they were exiled and dispersed. The sentiment has found many expressions throughout Jewish history and is too well known to require repeated documentation, but a few examples may remind us of its ardent nature.

“By the rivers of Babylon, there we sat down, yes, we wept, when we remembered Zion,” opens a well-known Psalm (137). And the weeping does not meander into a passive nostalgia, but leads to an active determination expressed in the oath: “If I forget thee, O Jerusalem, let my right hand forget her cunning.” When the moment of return from Babylon arrives, the experience transcends the confines of reality: “When the Lord turned again the captivity of Zion, we were like them that dream.” (Psalm 126).

Goethite, lepidocrocite and hematite were reacted with glycerol and reaction products were studied at various steps of the reaction. After a treatment of 16 hr at 245°C the final form of the reaction product, a deep green soft solid, was obtained whatever the starting material. According to hydrolysis and chemical analysis, the reaction product can be identified as iron alkoxide. Hydrolysis of the solid by boiling water yielded glycerol and a strongly magnetic material characterized by a spinel structure like maghemite and magnetite.

The iron alkoxide is seen by electron microscope as large well-formed hexagonal platelets. The similarity between a and b parameters of this compound and those of brucite suggests that the iron alkoxide structure is based on an iron (II and III) octahedral layer. The glycerol chains should be located between the sheets. Two models were proposed in which iron and oxygen, linked to the chain of glycerol, could be accommodated in octahedral layers giving a basal distance of 8·1 Å.

At least two steps are involved in the formation of the iron alkoxide: (1) a rearrangement of the structure of the starting material with accomodation of carbon in the structure and (2) a reduction of ferric iron.

The problem to which this article tries to supply an answer, in any case for the time being, is the following: was the political collapse of the Greek world the result of a slow internal disintegration or of the destructive action of the Roman conquest?

In other words: did the Graeco-Macedonian states, constituted after the conquest of Asia by Alexander, die ‘their own splendid deaths’ or were they ‘assassinated’ by Rome?

History records innumerable assaults by the barbarian nomads of the steppes and deserts on the realms of civilization. In some cases, the invaders overturned an organized state, as the Hyksos did Egypt, the Ephthalites northern India, and the Kin northern China. In others, they were thrown back, as the Huns were from the Roman Empire and the Avars from Byzantium and Frankland. Some shed their barbarism and acquired the arts of civilization, like the Magyars and the Ottoman Turks, others remained illiterate pastoralists to the end, like the Scythians and the Cumans. Two created world empires as a result of conquests the scope and magnitude of which still grip the imagination. These were the Arabs of the seventh century and the Mongols of the thirteenth, whose spectacular achievements pose problems concerning the interrelationship of nomadic and sedentary societies and of the nature of the “drives” which impel pastoral peoples to burst out of their homelands not simply to raid and plunder but to establish political domination over their civilized neighbors. The Arab and Mongol conquests also raise the question why the former cleared the ground for the erection of a distinctive new world culture and the latter did not.

Mössbauer spectra of 15 smectites were investigated. In these samples, ferric iron occupies both M(1) and M(2) octahedral sites, the distribution being partly determined by the relative covalency of the bonds formed.

The quadrupole splittings are linearly related to b−3. They show that Fe3+ octahedra are much more distorted in montmorillonite and beidellite than in nontronite and volkonskoite and that M(1) sites are more prone to change than M(2). Ferrous iron occurs in relatively undistorted octahedra in some otherwise distorted octahedral sheets and vice versa.

In this paper we discuss sudoku-solving strategies and how graph theory can be used to explain some of the advanced techniques. There are many websites that provide tutorials on solving sudoku puzzles. The sites [1] and [2] discuss the xy-chain technique, and the two explanations are quite different. We will define xy-chains as paths in a graph, and properties of the paths show why the technique works.

No other culture, no other epoch has portrayed nature with as much nostalgia, has projected, discovered and venerated in nature so rich a complex of meaning as the one which, gradually and paradoxically, ended by sanctifying history. Around the time of the French Revolution the frontiers of the universe suddenly seemed to melt away into infinity: the emancipation which the Enlightenment had worked in the domain of religion, philosophy, morality, education was a prelude to the inauguration of a new world which, with the effervescence of a spring wine, flooded the carefully delineated and organized landscape of traditional humanism. The powerful wind of Sturm und Drang now blew across the world, closed and arranged like a garden, in which man had hitherto seen the theater of his actions and his sentiments. From Rousseau on nature is no longer the enemy of the spirit, but the life-giving force of a world fulfilled in and for itself. No longer does nature draw its movement and meaning from man, but on the contrary it obliges him to strain his limited forces and pushes him out of himself and toward the great Whole, the ἕν καὶ πἇν from which he had painfully torn himself.

This article was based on a presentation that was given at the IFLA-Art Libraries Section Satellite Conference. In an effort to push toward a more multidisciplinary and holistic approach to the data generated throughout the National Gallery of Art in Washington, DC, staff have been investigating new ways in which to amass, organize, and use that data. Segueing from a GIS mapping initiative, one such project sought to amalgamate disparate kinds of data centering around pigment analysis. This led to a multidepartment team trialing software solutions, raising questions and identifying challenges about how the institution creates and standardizes its data, and what changes are needed as we look to the future.

Feedback appears to be a fundamental characteristic of the phenomena of life. Elsewhere it only appears in man-made machines. These machines are always presented as being a meeting ground for laws immanent both in matter and in man. A new science has been created to study the applications of feedback: cybernetics. As feedback is closely related to questions concerning the transmission of information, cybernetics has rapidly given rise to a theory of information. The latter, with its applications, has taken on an absolutely essential role in our modern world wherever problems of administration occur.

On NH4- as well as on (C2H5)3NH-montmorillonite EDA was adsorbed in protonated form. The extent of protonation depended on the relative basicities and concentrations of the interacting compounds. In the systems exposed to EDA vapor a proton transfer process took place. A similar mechanism, involving probably a water molecule which remained associated with the EDAH+ ion, occurred on air-drying (C2H5)3NH-montmorillonite treated with aqueous EDA, whereas no adsorption was observed when the suspension was washed. On the contrary EDA added, in quantities not exceeding the CEC, to a suspension of NH4-montmorillonite was adsorbed almost exclusively as EDAH22+ ion. This is explained in terms of ion-exchange between NH4+ and EDAH+ present in aqueous medium and protonation of the second amine function through the dissociation of water molecules near the clay surface.

Hydrogen-bonding between protonated and neutral EDA was observed when the extent of adsorption was higher than the extent of protonation.

Being is, above all, a vocation to continue to be. In the inanimate world, pure inertia achieves this ambition by means of its insistence on maintaining every conceivable state of equilibrium or else of movement. That which is persists in remaining as it is; a stone, for instance, insofar as nothing prevents it from continuing to exist in its condition as a stone. Certainly, this is the earliest and most remote origin of that which, at a later stage, is destined to manifest itself in art in a form that is not recognizable; in this case one might well say that, in the Beginning, was Classicism.

A golden-colored, flaky mineral from Morro do Niquel, Minas Gerais, Brazil, gives an X-ray diffraction pattern of a IIb chlorite polytype, with basal spacing 14·21 ± 0·02 Å and b = 9·23 Å. Thermogravimetric analysis shows a progressive weight (water) loss up to 500°C, followed by a rapid weight loss corresponding to dehydroxylation of the interlayer material and a slower weight loss due to dehydroxylation of the 2:1 layer. The structural formula derived from the chemical analysis on the basis of O10 (OH)8, or total cation valence of +28, shows 5·3 total octahedral cations, i.e. probably 2·3 in the interlayers where normally 3 cations are found. This deficiency together with the appreciable loss of water below 500°C suggests a partially vermiculitized interlayer. A new method for deriving the interlayer composition gives R1·67(OH)4·08(H2O)0·59, and a ratio (OH + H2O)/R = 2·80, which approaches that of a dioctahedral interlayer and is consistent with a predominance of R3+ ions. The mineral may resemble the golden, vermiculitized biotite described by Walker and others.

The thickness of the two-layer ethylene glycol complex of dioctahedral smectites varies under room conditions between 17.3 and 16.5 Å because of such factors as layer charge density, type of interlayer cation, and relative humidity. Neglecting this variability can give up to 30% error in the X-ray powder diffraction estimation of the smectite:illite ratio of the mixed-layer structures. Three methods have been developed for the interpretation of X-ray powder diffraction patterns of glycolated mixed-layer illite/smectite which take layer-spacing variability into account. The methods include a technique for quantifying the degree of layer ordering. In addition, the proposed techniques minimize the error due to the influence of domain size on positions of reflections. The experimental error can be kept below 5% or below 1% smectite layers, depending on the method applied, provided that the peak positions are measured with the accuracy of ± 0.02°2θ.